Electrode for thermionic discharge devices



i March 30, 1937; c. w. cAsTLE ELECTRODE FOR THERMIONIC DISCHARGE DEVICES Filed Jan 25 1935 INVENTOR C. W. CASTLE BY %M% ATTORNEY Patentetl Mar. 30 1937 I PATENT OFFICE ELECTRODE FOR. THERMIONIC DISCHARGE Chester W. Castle; Maplewood, N. J., assig nor, by mesne assigmnents, to Radio Corporation of America, New York, g Delaware N. Y., a crporation of Application January 25, 1935. Serial No. 3,497

. 3 Claims.

My invention relates to improvements in electrodes for electron discharge devices, and more' particularly to grid electrodes.

Multi-electrode thermionic discharge devices are well known i'n which there is mounted within an envelope a cathode surrounded by concen-j- 'trically positioned grids, and an anode. In a i well known screen grid type of tube i'or example,

there is a tubularinner screen inside the tubular anode, and anouter tubular' screen surrounding -the anode and Suspended at 'its upper end from a plate or so-called top shield. This cylindrical outer screen is secured to the top plate by clinching its upper edge under a flange at the outer edge of the top plate. 'The 'usual' practice is to make this cylindrical outer screen of a sheet of woven wire mesh or punched sheet metal which is rolled into cylindrical form and the ends joined,

either by welding or by folding the' ends back` upon each other to form a lock seam with interlocking fianges. Welding is rather expensive in view of the relatively slow processing thru which the screen grid must be put. With a lock seam difllculty has been experienced in positioning and clinching underthe flange of the top plate the 5 relatively thick seam, which includes four thick-.

nesses of the screen grid stock. The lock seam, further, provides between the connected portions u of the screen stock only a. pressure contact which O is' found to be undesirable especially in high frequency operation. I

An object of my invention is to provide a tubular electrode element tor a thermionic discharge device which is simpler in construction and 'easier 5 and less expensive to manufacture than the elecp grid electrode is-formed by overlapping the ends of the sheet of screen stock and securing the .overlapped ends together by pressing themtogether with suflicientforce to press the material 50 of 'one end of the cyllndrical stock into recesses in the material oi' the other end.

.For a better understanding of my invention,

however, reference may be had to the accom-' panying drawing in which Figura 1 shows the 55 'conventional lock seam screen grid; Figur-e 2 is a 'In accordance with my inventioi the tubular perspective view and Figure 3 an end view oi a screen grid embodying my invention; and Figure 5 shows a modified pattern of my seam; and.

. Figure 4 shows in section and Figure 'ia in plan a portion oi' my seam constru'cti'on.

In many tube constructions in which a. plurality of cylindrical g'rids are used, it is customary to support one of the grids, for example the cute: screen, from a top plate or metal disc which is shaped much like the cover of a tin can and is secured to the upper end'of the electrode assembly; The cylindrical tubular screen, of a di ameter equal to that 'of the top plate, is con venieritly secured to the lower side o the top 'plate by simply fitting the upper edge ot'the cylindrical screen into the top plate. .This construction is shown diagrammatically in the 'upper part'of Figure 2 of my drawing. This construction is simple and cheap, but the usual four thicknesses of stock at the lock seam made as shown in Figura 1 causes dimculties in assembling the screen and top shield.

As shown in Figures 2 and 3, my improved screen electrode comprises a cylinder 'l formed multi-pointed hammer is caused to strike the seam at spots or areas I l, whereby the material of the cylinder, which is preferably woven of nickel or other ductile metal, is compressed to such an extent that the individual wires or strands thereof are forced to flow into the recesses and spaces of the other overlapped end v 'of the stock. So complete is the upsetting or the metal at the hammered portions of the seam. 7 the finished product appears to besubstantially of solid metal and' free'from openings. .By the swaging action 'of the hammer the compressed portions' of the wire stock appear to resemble ing.

may, according to my invention. be formed into 'any desired pattern. In Figure 5, for example 'der' 'I' is 'slipped over a rounded mandrel and a' stock along the longitudinalcenter line of the The surface of the pressed portions of the sea m' solid sheet metal, the edges 'of which merge into the individual wires 'or strands oi' thewire screenscreening stock are forced into the swaged areas of the seam. It is obvious from this construction that the seam is further strengthened.

Referring to Figures 4 and 4a, the swaged portion of the seam is shown in detaii which clearly illustrates the manner in which the individual strands of the wire screening 3 and 5 are overlapped and' flattened out to form continuo'us impervious mass ll of sheet metal.

One method ot ioining the shield to its sup.- porting plate may be understood by reierring again to Figure 2, the upper part of which reprewithin the flange IS so as to produce a. strong and neat appearing connectiom This difliculty, however, is overcome' by the screen made in accordance with my invention, since the seemed portion of the cylinder is of the 'same thickness as, or less than the thickness of, one layer ot the stock. This provides a. smooth connection between the grid cylinder andits top plate which is neat in appearance and strong in construction.

while the seam is uniform in manufacture and. provides good electrical contact between the end portions of the screen stock.

It will be obvious to those skilled in the art that many modiflcations may be made in mydevice without departing from the spirit of the invention. It is accordingly. desired that my invention be limited only by 'the prior art and by the appended claims.

What I claim as new is:-

1. In the art of seaming a wire mesh screen, the method comprising overlappingtwo portions of the screen to be seemed, and swaging spaced portions of the screen along the overlapped seam.

' 2. In the manufacture of thermionic tube electrodes formed of a wire mesh screen, the method comprising, rolling the screen to form a closed annulus, overlapping the ends of the annulus, and applyingforce to opposite sides and at spaced portions of the overlap to swage the wires u at said portions into flat substantially impervious sheets of metal of parallelogram surfaces.

3. In the manufacture of a thermionic tube electrode of the screen sheet type, rolled into the form of a cyiinder, the method comprising overu lapping the ends of the sheet material; and applying suflicient force to the overlapped material at spaced areas along`the overlapped portion to interieave the component parts at said areas ot the 'overlapped portions.

' CHESTER W. CASTLE. 

